Borax as an efficient metal-free catalyst for hetero-Michael reactions in an aqueous medium

Borax, a naturally occurring material, very efficiently catalyzed the conjugate addition of thiols, dithiols and amines to alpha,beta-unsaturated ketones, nitriles, amides, aldehydes and esters in an aqueous medium to afford the corresponding Michael adducts in good yields at room temperature. Recycling of the catalyst and scaling up of the reactions are important attributes of this catalysis. The reactions of thiols and dithiols were relatively more facile than those of the corresponding amines. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).